1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * custom_method.c - debugfs interface for customizing ACPI control method
4 */
5
6 #include <linux/init.h>
7 #include <linux/module.h>
8 #include <linux/kernel.h>
9 #include <linux/uaccess.h>
10 #include <linux/debugfs.h>
11 #include <linux/acpi.h>
12 #include <linux/security.h>
13
14 #include "internal.h"
15
16 #define _COMPONENT ACPI_SYSTEM_COMPONENT
17 ACPI_MODULE_NAME("custom_method");
18 MODULE_LICENSE("GPL");
19
20 static struct dentry *cm_dentry;
21
22 /* /sys/kernel/debug/acpi/custom_method */
23
cm_write(struct file * file,const char __user * user_buf,size_t count,loff_t * ppos)24 static ssize_t cm_write(struct file *file, const char __user * user_buf,
25 size_t count, loff_t *ppos)
26 {
27 static char *buf;
28 static u32 max_size;
29 static u32 uncopied_bytes;
30
31 struct acpi_table_header table;
32 acpi_status status;
33 int ret;
34
35 ret = security_locked_down(LOCKDOWN_ACPI_TABLES);
36 if (ret)
37 return ret;
38
39 if (!(*ppos)) {
40 /* parse the table header to get the table length */
41 if (count <= sizeof(struct acpi_table_header))
42 return -EINVAL;
43 if (copy_from_user(&table, user_buf,
44 sizeof(struct acpi_table_header)))
45 return -EFAULT;
46 uncopied_bytes = max_size = table.length;
47 /* make sure the buf is not allocated */
48 kfree(buf);
49 buf = kzalloc(max_size, GFP_KERNEL);
50 if (!buf)
51 return -ENOMEM;
52 }
53
54 if (buf == NULL)
55 return -EINVAL;
56
57 if ((*ppos > max_size) ||
58 (*ppos + count > max_size) ||
59 (*ppos + count < count) ||
60 (count > uncopied_bytes)) {
61 kfree(buf);
62 buf = NULL;
63 return -EINVAL;
64 }
65
66 if (copy_from_user(buf + (*ppos), user_buf, count)) {
67 kfree(buf);
68 buf = NULL;
69 return -EFAULT;
70 }
71
72 uncopied_bytes -= count;
73 *ppos += count;
74
75 if (!uncopied_bytes) {
76 status = acpi_install_method(buf);
77 kfree(buf);
78 buf = NULL;
79 if (ACPI_FAILURE(status))
80 return -EINVAL;
81 add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
82 }
83
84 return count;
85 }
86
87 static const struct file_operations cm_fops = {
88 .write = cm_write,
89 .llseek = default_llseek,
90 };
91
acpi_custom_method_init(void)92 static int __init acpi_custom_method_init(void)
93 {
94 cm_dentry = debugfs_create_file("custom_method", S_IWUSR,
95 acpi_debugfs_dir, NULL, &cm_fops);
96 return 0;
97 }
98
acpi_custom_method_exit(void)99 static void __exit acpi_custom_method_exit(void)
100 {
101 debugfs_remove(cm_dentry);
102 }
103
104 module_init(acpi_custom_method_init);
105 module_exit(acpi_custom_method_exit);
106